The present invention relates to a power plant.
An example of power plant is an ocean thermal energy conversion (hereinafter referred to as OTEC) plant, which utilizes warm surface seawater (e.g., of 25.degree.-30.degree. C. ) as a high temperature heat source and cold deep seawater (e.g., of 5.degree.-7.degree. C.) in the depth of several hundreds to about a thousand meters, as a low temperature heat source, and has a Rankine cycle operated by the temperature difference (of about 20.degree. C.) to drive a turbine.
The high temperature heat source of this type of plant is dependent on the sun. In the equatorial sea area, the temperature of the surface seawater is high and its seasonal change is small, so that the equatorial sea area is ideal for this type of plant. In contrast, in the high latitude area including Japan, the temperature of the surface seawater varies largely depending on the seasons and is low in winter causing substntial reduction in the turbine output. For example, decrease of the temperature by 1.degree. C. causes as much as 50% reduction in the turbine output. For this reason, OTEC plants in the high latitude area, even those of most favorable location, can be operated only in several months a year. Therefore, the utility factor of the equipment is low and the system is not economical.